The present invention relates to a rotor for tacho-generators, particularly for direct-current tacho-generators, having axial grooves arranged at the rotor circumference for receiving rotor windings which each enclose one or several teeth formed by the grooves at the circumference of the rotor.
Tacho-generators with corresponding rotors are used for generating a voltage that is proportional to the respective speed of the rotor. In direct-current tacho-generators, the voltage generated in the windings by magnetic induction is collected via collectors, by carbon brushes or the like.
In conventional tacho-generators, the rotor consists of a bundle of bars which are arranged axially behind one another. In addition, the teeth formed between the grooves are preferably constructed as so-called pole pieces, so that the grooves narrow in the direction of the outer circumference of the rotor while forming very narrow gaps.
This rotor construction corresponds to the method of construction of power generators. This known construction is therefore optimally designed with respect to the magneto-dynamic conditions.
Because of the narrow gaps between the teeth, the arrangement of the rotor windings becomes extremely difficult. In addition, the generated voltage has harmonic waves so that, as a rule, relatively costly circuit arrangements are required for the smoothing of the voltage. On the whole, the conventional method of construction is therefore costly.
It is an objective of the present invention to provide a rotor that is particularly well suited for tacho-generators and is produced with significantly reduced manufacturing expenditures.
This and other objectives are achieved in the present invention by the provision of a rotor comprising at least one massive disk made of a ferromagnetic material, such as iron or steel, for example. In certain preferred embodiments, the rotor comprises a few corresponding disks.
The invention is based on the recognition that a tacho-generator, in contrast to a power generator, does not have to be designed for a performance that is as high as possible. In contrast, what is important is an optimal quality of the generated voltage, particularly of a direct-current voltage, i.e., the most extensive freedom from harmonic waves and voltage peaks. In addition, a good linearity should exist between the generated voltage and the respective speed, such that the generated voltage rises as linearly as possible with the speed.
This requirement is met much better by the integral and largely homogeneous disks than by a bundle of bars. This is due essentially to the fact that the massive monolithic material of the integral disks can be magnetically reversed only with a comparatively high inertia. This effect that is extremely undesirable in power generators, according to the invention, is therefore utilized for the optimization of a tacho-generator. It is particularly advantageous for the rotor to comprise only one single massive disk.
As a result, an essential advantage is achieved that the costs for the manufacturing of the rotor are reduced considerably. The rotor, according to a preferred embodiment of the invention, may also be manufactured by powder metallurgy.
In addition, in certain preferred embodiments, the grooves, in axial view of the rotor, are clearly wider than the teeth, for example, at least twice as wide. According to a preferred embodiment, the ratio of the widths of the tooth faces to the widths of the grooves are approximately 0.3.
In these embodiments, the arrangement of the coil windings is extremely facilitated. In addition, the quality of the direct current that can be generated is also improved again.
In a particularly preferred embodiment, the tooth profiles, in the area of the outer circumference of the rotor and in axial view of the rotor, are beveled in the corner areas in the manner of chamfers. As a result, it is ensured, in a particularly simple way, that a central radial plane of each rotor winding extends outside the teeth that are directly adjacent to the rotor winding. Because of this construction, the coils may be wound directly onto the rotor, without any deflecting plates and baffle plates or the like.
In order to hold the coil windings on the rotor in a particularly secure way, the tooth profiles of each tooth are sloped in certain preferred embodiments, with respect to one another in axial view of the rotor such that the tooth is slightly widened radially toward the outside.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.